So in gemfile :

gem 'delayed_paperclip'    , '2.4.5.2', :git => 'git://github.com/tommeier/delayed_paperclip', :branch => 'fix_312'

Good point @timols, i'll update now.

Removed unnecessary line and made sure a test checks the resulting value in case paperclip changes their API.

The redefinition of the most_appropriate_url doesn't work for me, it's still the original Paperclip::UrlGenerator one that is called. Also why not just creating a new UrlGenerator inheriting from Paperclip::UrlGenerator? You could just modify the default options to use it then. Here's what I did in my app:

module Paperclip
  class MyUrlGenerator < UrlGenerator

    def for(style_name, options)
      escape_url_as_needed(
        timestamp_as_needed(
          @attachment_options[:interpolator].interpolate(most_appropriate_url(options), @attachment, style_name),
          options
      ), options)
    end

    private

    def most_appropriate_url(options)
      if @attachment.original_filename.nil? || (!options[:without_processing] && @attachment.delayed_default_url?)
        default_url
      else
        @attachment_options[:url]
      end
    end
  end
end

And then in my model

Class Image < ActiveRecord::Base
    has_attached_file(:resource, :url_generator => Paperclip::MyUrlGenerator, ... )
    ...
end

Oh, I also had another problem with your patch, you can't call reprocess! directly anymore, it won't do anything, you need to call process_delayed!. Maybe more a note than an issue as it's not something you want to call too often.

@bastien good idea, just want to work out a cleaner way to make it apply across the board when using delayed_paperclip, didn't have time to sort it out, so the quick hack won in the end unfortunately.

Calling reprocess! is working fine in prod for us?

@tommeier is it because you set the attachment post_processing to true manually?